1. Length of the Seasons Venus Transit June 8th, 2004 The Universe Dr. Scott Schneider Friday April 23 rd, 2004 Presentation for National Astronomy Day Presentation for National Astronomy Day (technically 04/24/04) Webpage : http://www3.ltu.edu/~s_schneider/astro/astroday_2004.shtml

2. Lengths of the Seasons change Earth orbit is “drifting” around the Sun –Precession of orbit Caused by pull from planets and Moon –Close/Far points in orbit move We adjust calendar with leap days –To prevent snow in July! But duration of seasons oscillate

3. How to find your way in the Solar system : All planets go around the Sun –also, in the same “direction” Define reference plane as Earth-Sun –Called the ECLIPTIC –All other planet orbits tilted, relatively Venus has an orbit tilt of about 3 0 –Save this info for later!

4. Seasons vs. Aphelion/Perihelion Spring defines quadrants Quadrants near Aphelion are longer in time Perihelion and Aphelion drift – so season lengths change

5. Season duration – short time scale Currently Spring/Summer are longer –But, Spring duration shrinking.. Fall rising!

6. Season duration – long time scale Winter longest before –4000 (shortest ~3500)

7. Follow Spring Equinox Date (wide) Spike around 1600? – Gregorian Reformation!

8. Follow Spring Equinox Date (med) Small shifts at 100, none at 2000, 2400, 2800??

9. Follow Spring Equinox Date (zoom) Slow drifting of the date later in March

10. More info on seasons? http://www3.ltu.edu/~s_schneider/astro/seasons.shtml (Unlinked to show the underscores …) http://www3.ltu.edu/~s_schneider/astro/seasons.shtml

11. What is a transit? Planet crosses the face of the Sun Mercury and Venus = closer to the Sun –occasionally pass between Earth + Sun Transit of Earth for the Moon? –Lunar eclipse Transit of the Moon seen by the Earth? –Solar eclipse!

12. Features of Venus Transits Nearly circular orbit –Transits at each node in equal numbers Mercury : Less often in May than November –Moving faster in orbit in May Only seen from part of the Earth –Usually a whole hemisphere –Sometimes “grazing” – only part of hemisphere 243 year cycle (with 8 year and ~ 100 shifts) Venus “large” enough to see “naked” eye –Must use eclipse glasses or protected scope!eclipse glasses

13. Rarity of Venus Transits? Between –2000 and 4000 – only 81 No human alive has seen one (1882) Transit of 1631 predicted by Kepler –But not seen! Currently occurs in June or December –Usually occur in pairs – 8 years apart Because 13 revolutions of Venus ~ 8 of Earth –Another period of ~105-110 years –Strong period of 243 years (forms “series”)

14. Historical notes of Transits Mercury ~ 1/158 to 1/195 of Sun’s disk –Not seen without a telescope! Venus ~ 1/31 to 1/32 of Sun’s disk –Visible w/o telescope (but with FILTER!) Venus transits widely observed in late 1700’s and 1800’s

15. Ecliptic plane - Today Oriented by Seasons (Spring = pivot) Venus orbit = Blue = above … Green = below (nodes) SPRING WINTER FALL SUMMER

16. Ecliptic plane – at Transit Oriented by Seasons (Spring = pivot) Venus orbit = Blue = above … Green = below (nodes) SPRING WINTER FALL SUMMER

17. Right place - Right time! Venus makes more orbits than Earth Often passes those crossing points (nodes) –But, Earth isn’t always there to see it! One “face” of the Earth gets best view –Transit is at most ~ 8 hours Short time scale - not a good match –Wait many years, orbits match nicely!

18. What does “a pass” mean? Nov/Dec transits - lower left to upper right May/June transits upper left to lower right As the “cycle” advances, individual passes will move either “up” or “down” relative to the center of the sun A “series” would be a set of passes

19. How would a “series” look? Full Series “B” 243 Year period

20. What about a “pair”? 8 year jump between consecutive series

21. Can I investigate the transits myself? Sure! Here is the website for my very first home-grown Java applet – the Venus Transit applet! http://www3.ltu.edu/~s_schneider/astro/transits/venusjava.shtml (Unlinked to show the underscores …) http://www3.ltu.edu/~s_schneider/astro/transits/venusjava.shtml

22. Tuesday, June 8th, 2004 Circumstances for Detroit: Sunrise 05:54 AM (Venus past midpoint of transit) –Venus rises a few minutes later (tip of sun = “sunrise”) Venus touches inside edge of sun (on way out) = 7:05 AM at 11 degrees above the horizon Venus touches outside edge = 7:25 AM at 14 0 alt Possible trip to Metro Beach MetroPark? –(Better view of sunrise) Wear your glasses!! Great prediction webpage : http://sunearth.gsfc.nasa.gov/eclipse/transit/TV2004.html http://sunearth.gsfc.nasa.gov/eclipse/transit/TV2004.html

23. But can we really see it? Luckily, we have a sunspot today (04/23/04) – it is a little smaller.. and we can see IT!

24. References Jean Meeus – TRANSITS – Willmann-Bell Jean Meeus is an Astronomer from Belgium – does some absolutely amazing astronomical calculations. Has three other excellent books : Astronomical Algorithms Astronomy Morsels More Astronomy Morsels

25. What about Marvin? He wanted to blow up the Earth because it blocked his view of Venus!

26. Conditions for blocking.. How often does Earth block Venus? Calculate the location where the Venus-Mars line crosses the ecliptic – if the Earth is there also – block!

27. After the computer pulled a few all-nighters … From the year 1000 to 3000 … Only one time = Nov 8 th, 2746 ~ 7:45 pm

28. Conclusion … Marvin is just a big foo-foo head!!

29. Last but not least … The Universe! Logarithmic distance scale (y axis) –Need strong kung-fu math to squash the distance scale of the Universe! “Hour angle” (right ascension) (x axis) –Measured from “Spring” event – (line in space) –360 degrees = 24 hours The Universe on the Second Floor! Much more info here : –http://www.astro.princeton.edu/~mjuric/universe/http://www.astro.princeton.edu/~mjuric/universe/

30. Astro Wall Volunteers James Mason * Clark Adamczyk * Steven R Moberly * George Swan * Lindsay Zaremski Adrian Brdarski Jeremy Dunaj Judy Sullivan (Custodian) – Cleaner of the Solar System! * Members of LTU’s first undergraduate Astronomy course These students helped me put little dots on the wall, and big giant strips of tape.

31. This talk, and other exciting things can be found … http://www3.ltu.edu/~s_schneider/astro/index.htm Thank you, Good Night, Drive Safely!